Exogenously expressed granulocyte colony-stimulating factor (G-CSF) receptor on K562 cells can transduce G-CSF-triggered growth and differentiation signals.

Human granulocyte colony-stimulating factor (G-CSF) receptor cDNA was introduced into the erythroleukemic cell line K562, which normally does not express the receptor, using lipofection transfection of a G-CSF receptor expression plasmid vector. Transfected cells expressed the receptor with a dissociation constant of 130 pmol/L, and a maximum of 11,800 binding sites per cell. Culture of G-CSF receptor-expressing cells (GR-K562) in the presence of G-CSF enhanced DNA synthesis and a stimulation index of 4.61 was obtained in a 3H-thymidine uptake assay. Furthermore, flow cytometric studies revealed induced expression of CD11b (29% from 7%), and enhanced expression of CD13 (57% from 27%) on GR-K562 cultured in the presence of G-CSF. Our findings indicate that the exogenously expressed G-CSF receptor can deliver signals and function efficiently on these immature cells on which the receptor is not normally expressed, which suggests the presence of intact intracellular signal transduction pathways that can be used by the ectopically expressed receptor.